Salad dressing

Salad dressing is a sauce, which is used to make an entire salad tastier. A dressing is an oil-in-water emulsion and generally consists of a combination of oil, water, vinegar, citric acid, salt, spices and an emulsifier. A thickening agent, like xanthan gum or carrageenan, is often added to the low-fat salad dressings.

There are two main types of salad dressings:

  • Spoonable salad dressing:
    Traditionally, this is mayonnaise with a fat content of at least 75%
  • Liquid salad dressing:
    Liquid salad dressings can be either homogeneous or in two layers.

The dressing with two layers must be shaken before use, to mix the two layers. In general, liquid salad dressings have a low pH between 3,5 and 3,9, which is the reason they keep fresh longer than spoonable salad dressings. A typical liquid salad dressing is vinaigrette.

These two types of salad dressings are produced in many different tastes and nowadays the low-fat varieties are produced more and more.

The production of the liquid salad dressing will be described below.

Production salad dressing

Raw materials

The basic ingredient in salad dressing is oil, like olive, soya or sunflower oil. To obtain the required viscosity and stabilise the emulsion, stabilizers or thickening agents are added, such as modified starch. Depending on the type of salad, also other ingredients can be added such as different spices, eggs, citric acid, vinegar, salt, sugar and for a homogeneous dressing, an emulsifier.
When vegetables and spices are in the salad dressing, generally blast-frozen vegetables and spices are used.


The mixing starts with water. To this water the ingredients salt, vinegar and modified starch are added. The whole is mixed and heated to approximately 90°C, in order for a starch paste to form. The whole is then cooled and the remaining ingredients are added, such as spices, eggs and sugar.


To get the desired emulsion, a continues mixing system is often used nowadays.
However, a colloidmill can also be used. The procedure is then as following: after the mixing, oil is slowly, while stirring, added to a part of the formed starch pasta. When approximately half of the oil is added, the remaining part of starch paste is also added, as slowly as the oil is being added. When the whole is mixed properly, it is lead through the colloidmill, to obtain an emulsion with a uniform consistency.


The emulsified salad dressing is pumped to the bottling station. Here, pre-measured amounts of salad dressing are dropped in pre-sterilized jars or bottles and these containers are immediately sealed with metal or plastic caps.
The containers are then labelled, packed in boxes and stacked on pallets.


Due to the low pH of the salad dressing, it will remain fresh for a long period of time. However, after opening, the salad dressing must be kept in the refrigerator.


New standard for hygienic cabling in machine construction?

Can a machine building company make a substantial contribution to the optimisation of the process industry? This practical story from the world of mechanical engineering shows this is indeed possible. Selo Food Processing and Packaging Systems succeeded in developing and marketing an innovation that could become a new industry standard for hygienic cabling in machine building. What was needed for that? A progressive customer, a contributing supplier, involved employees and an innovation-oriented director who dares to stick his neck out.

Selo delivers smart, custom solutions for the process industry - from design to commissioning at the customer’s premises. With more than 100 employees Selo are developing complete and ready-to-use processing and packaging systems, with integrated machine controls, from their headquarters in Twente, Hengelo. They do that well, because their expertise in process engineering and automation, engineering, control, assembly and installation is appreciated by leading international clients. One of the most progressive Dutch customers asked Selo to develop three process installations, that would make the use of cable ties (tie wraps) superfluous and would therefore be considerably easier to clean.

Streamline HD application by Selo Food Technology BV

Selo took up the challenge, searched for a suitable solution and approached Gouda Holland, a manufacturer and supplier of cable guidance solutions. Under the flag of parent company, Niedax Group, Gouda Holland developed a hygienic and sound system for field and machine cabling that started a true advance in the process industry under the brand name Streamline HD. Willibrord Woertman, Director Selo: "Our Electrical and Software Engineer Erwin van Buren pointed out this system, on which we based the further development of our new, food- safe and user-friendly cable routing for process installations.”

Hygienic cabling in a nutshell

Anyone who uses recent guidelines for hygienic cabling soon realises that the time of the closed cable ducts is now behind us. Open, accessible and optimally cleanable is the new motto. As a result, machine builders switched over to the use of wire channels for cable routing. However, hundreds of cable ties are installed per installation to secure the cables to the wire channels. Selo's clients wanted to get rid of those cable ties, because they prevent optimum cleaning of the process installation and in the worst case scenario they can even break and end up in the food processing process.

Woertman: "This cable routing system makes the use of cable ties unnecessary because it has fixable spirals for the tool-free fastening of individual cables. Hygienic, convenient, user-friendly and time-saving. In collaboration with Gouda Holland, we have integrated the system into our design. That was quite a change. Where cable routing used to be determined in the construction phase, it had to be included in the design during the engineering phase. We then further perfected the cable routing in every new version of the ordered process installations.”

Include cabling in the design as early as the engineering phase

Bert Erdtsieck, Manager Sales at Gouda Holland: "Applying Streamline HD to a process installation - that was a new challenge for us. A process installation offers much less room for cable routing than a factory hall for field cabling, so we had to miniaturise components and examine how we could use our existing production facilities. Based on Selo's specifications, we first developed a prototype that we presented to all employees. The first reactions were disappointing, especially the mechanics who initially reacted cautiously. Although they saw the functional benefits for the end-user, the assembly cost them more time than they were used to. Selo continued to support the initiative and proposed to adapt the entire workflow and integrate the Streamline HD components into the pre-engineering of the design. . As a result, when assembling the second process installation, the mechanics knew in advance exactly where and how the components should be placed.”

Innovation-oriented leadership

The employees of Selo recognise the value of the innovation-oriented leadership of their management, but are also very knowledgeable and empowered. That is why the management must provide convincing arguments for every process change. Woertman: "Innovation is a fundamental strategic choice for us: a business strategy. Developing and marketing a new innovation requires persistence, initially everyone says: it is all too expensive, we lose too many hours with this, however, then you take a step back, overlook the entire process and realise there are all kinds of possibilities. By adjusting our internal work processes in this case, we reached a tipping point and after the completion of the most recent process installation everyone was convinced. Installing the Streamline HD components is now going much faster than before - the assembly time is halved compared to our conventional process. In addition, we gain extra time savings because the final cabling of the process installation is much faster and that times two: first in our own workshop and then when connecting field and machine cabling at the customer location. The initial extra time investment at the engineering phase resulted in a considerable productivity gain in the entire process. Our post calculation shows that the efficiency gains realised largely compensate the extra costs for the purchase of the more expensive hygienic design components and that means that our customers can integrate the hygienic cable routing in their process installations without significant additional costs. The ease of cleaning, food safety and user-friendliness of the process installation are available through Selo without significant additional costs. ”

Market advantage

According to Woertman, this project is a success for Selo in several respects: "The result of this innovation process confirms our vision that joint innovation pays off. We have not only been able to satisfy a valued customer, we have also created a concrete market advantage. At the Anuga FoodTec fair we presented a pilot unit that attracted a lot of attention. Everyone came to take a look and on the return journey from Cologne we received a lot of phone calls and messages. Everyone saw the benefits of our approach to food safety and productivity of food processing. The next step is to inform the food industry of these new possibilities, as this may be a new industry standard. Then we would really make a difference and contributed to food safety in the process industry.”

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Featured expert: Michael Evers

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  • Oils & fats
  • Salad dressing
  • Mixing
  • Emulsifying
  • Heating - cooling